In telecommunications network, SIP is one of many signaling protocols used to establish communication sessions between users and to provide supplementary services to the users. SIP is defined in IETF RFC 3261. One particular type of network that uses SIP is IP Multi-media Subsystem (IMS) Networks. IMS is defined by the Third Generation Partnership Project (3GPP) as a mobile network infrastructure that enables the convergence of data, speech, and mobile network technology over an IP based infrastructure. IMS bridges the gap between existing traditional telecommunications technology and internet technology, allowing network off-roaders to offer standardized, re-useable platforms that provide services using IP connected elements. The key IMS components that are used to provide telecommunications sessions and supplementary services are the Call Session Control Function (CSCF) and Home Subscriber Server (HSS). The CSCF is a proxy, which aides in set-up and management of sessions and forwards messages between IMS networks. The HSS holds all of the key subscriber information and enables users to locate and communicate with other users.
In telecommunications networks, subscribers are migrating from non-IMS devices to IMS devices. For example, a given network operator may have subscribers that use non-IMS terminals, such as CDMA terminals, and IMS terminals to communicate. In order for the network operator to support both non-IMS and IMS terminals, the network operator would either be required to have two parallel sets of network equipment that provide services to the IMS and non-IMS subscribers or to convert messaging between IMS and non-IMS protocols. One conventional method for supporting non-IMS or SIP subscribers is to provide a convergence server that receives tunneled IOS signaling from non-IMS terminals where the convergence server provides supplementary services to the non-IMS devices and to provide a separate set of IMS nodes that provide IMS signaling. This conventional solution is illustrated in FIG. 1. Referring to FIG. 1, when legacy terminal 100 seeks to access the IMS for a supplementary service, such as three-way calling, legacy terminal 100 first communicates with a femto cell node 102, which tunnels IMS signaling through the core IMS network 104 to a convergence server 106. Convergence server 106 communicates with terminal 100 using IOS signaling to provide the supplementary service. If the same network operator also has IMS terminals for which the operator decides to provide service, a separate set of IMS nodes must be used to provide that service. For example, in FIG. 1, if IMS terminal 108 seeks to access a supplementary service, terminal 108 contacts one of IMS application servers 110 and 112 via macro cell 114 and IMS core 104 using IMS signaling.
The solution illustrated in FIG. 1 is undesirable because same services are duplicated on convergence server 106 and IMS application servers 110 and 112. When the network operator moves to a pure IMS network, convergence over 106 becomes unnecessary and therefore a wasteful capital expense. In addition, when providing a standard service, such as voice calls, to legacy subscribers, the messages that are tunneled to convergence server 106 do not provide sufficient information to set-up the call, resulting in unnecessary signaling.
Another problem associated with IMS networks is the ability to identify non-IMS subscribers or devices to the IMS network. For example, in IMS networks, subscribers and devices are identified using SIP uniform resource identifiers (URIs). An example of a typical SIP URI is (phone number)@(IP address) or (operator domain). In contrast, legacy terminals use one or a combination of international mobile station identify (IMSI), mobile directory number (MDN) and equipment serial number (ESN) to identify subscriber terminals or devices. These legacy terminal identifiers cannot be used within the IMS core. However, these legacy identifiers must still be usable by legacy devices to identify themselves in non-IMS networks. Accordingly, there exists a need for a forwards and backwards compatible solution for identifying legacy devices to the IMS network.
Yet another problem associated with IMS networks involves excessive messaging associated with registration subscriptions. When an IMS terminal registers with an IMS network, the IMS terminal sends a register message to the IMS network. The IMS terminal also sends a subscribe message to the IMS network to subscribe to the status of the subscriber's registration. The IMS network maintains on a subscriber-by-subscriber basis, a registration subscription. When the subscriber subscription times out, the network sends a notify message to the subscriber notifying the subscriber that the subscriber is required to re-register. Requiring a network node, such as a femto cell node, to send subscribe messages for each subscriber registration can result in a significant amount of messaging between the femto cell node and the IMS network. Such messaging and the processing of such messaging can burden the network and the femto cell node.
Accordingly, in light of these difficulties, there exists a need for methods, systems, and computer readable media for providing services in a telecommunications network using an IOS/SIP adapter.